A MIDI to DMX converter box based on Teensy 3.

MIDI channel = DMX channel offset
Controller number = DMX channel (1-127 * offset)
Controller value = DMX value (scaled to 0-255)

Controller numbers 1-127 on MIDI channel 1 = DMX channels 1 to 127
Controller numbers 1-127 on MIDI channel 2 = DMX channels 128 to 254
Controller numbers 1-127 on MIDI channel 3 = DMX channels 255 to 381
Controller numbers 1-127 on MIDI channel 3 = DMX channels 382 to 508
Controller numbers 1-4 on MIDI channel 5 = DMX channels 509 to 512

MIDI channel = DMX channel offset
Note number = DMX channel (Starting at note 1)
Velocity value = DMX value (scaled to 0-255)

(See above mapping for note number to dmx channel conversion)

By using specially formatted sysex messages you can send the full DMX (0-255) resolution:

240 127 value_lsb value_msb channel_lsb channel_msb 247

To create the msb and lsb parts of an integer:

lsb = number & 127
msb = (number >> 7) & 127

To go the other way around we do:

number = (lsb & 127) | (msb <<7)